Vector-based waveform acquisition and display
Waveforms are acquired from a DUT into segments corresponding respectively to vectors of a vector pattern repetitively applied to the DUT. The waveform segments are displayed relative to vector numbers of the pattern to facilitate comparison of stimulus/response, debug, and other tasks. The relationship of the vector pattern is known relative to a trigger occurring once per repetition of the pattern, and vectors of the pattern are synchronous with a vector clock. The relationship of the time-domain waveform to the trigger is known. Taking account of these relationships and of system delays, each acquired waveform segment can be associated as it is acquired with a start-of-vector mark and with the corresponding vector number. Waveform displays are prepared which show the waveform segments corresponding to vector numbers of a user-selected range of vectors.
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Claims
1. A vector-based method of waveform acquisition and display, comprising:
- a. repetitively applying a sequential pattern of vectors to a device, each vector having a vector number and a period which is synchronous with a clock signal, and the pattern being synchronous with a periodic trigger pulse,
- b. detecting the clock signal and the trigger pulses,
- c. probing a net of the device to acquire waveform data,
- d. counting vector periods as the waveform data is acquired, and associating with each vector period a segment of waveform data acquired during that period, and
- e. displaying segments of the acquired waveform data along with indications of the vector periods with which the waveform segments are associated.
2. The method of claim 1, further comprising the steps of relating each vector period with a vector number and displaying the vector number with the waveform segment of the associated vector period.
3. The method of claim 1, further comprising the setup steps of:
- identifying values of (i) a vector number corresponding to a known state change on a net of the device, (ii) a vector number of a first full vector period after the trigger pulse is detected, (iii) a number of dock signal periods per vector period, (iv) duration of vector periods, and (v) vector numbers of repeated vectors and the number of repetitions of repeated vectors during each repetition of the pattern, and storing the identified values as setup data.
4. The method of claim 1, further comprising the calibration steps of:
- identifying the vector number of a vector period during which a known state change is expected on a net of the device,
- estimating a number of clock signal periods to count following detection of a trigger pulse to find the known state change,
- displaying waveform data acquired during an interval corresponding approximately to the estimated number of clock signal periods, and adjusting the estimated number of clock signal periods until the displayed waveform data includes the known state change,
- marking the position of a selected vector number relative to the known state change,
- determining values of (i) a system delay, (ii) relationship of the count of clock signal periods to vector numbers, (iii) relationship of clock signal periods to the trigger pulse and to vector periods, and (iv) first full vector period during which waveform data can be acquired, and
- storing the determined values as calibration data.
5. The method of claim 1, further comprising the steps of entering a range of vector numbers representing a set of vector periods during which waveform data is to be acquired and determining that waveform data is available for acquisition acquired during said range.
6. The method of claim 5, comprising the steps, for each vector period of said range, of:
- determining a number of clock signal periods to count following detection of the trigger to begin acquisition of waveform data,
- counting the determined number of clock signal periods, beginning acquisition of waveform data at the beginning of the next full vector period, and
- relating a segment of waveform data acquired during each vector period with a respective vector number.
7. The method of claim 6, further comprising storing the acquired waveform data segments with respective vector numbers.
8. The method of claim 1, further comprising the step of setting display parameters including number of vectors per display division and starting vector number of the display.
9. The method of claim 1, further comprising the step of setting a display option defining whether vector loops are to be included in the display.
10. The method of claim 1, further comprising the step of setting vector numbers for which waveforms are to be displayed.
11. The method of claim 1, further comprising the step of displaying start-of-vector marks with the displayed waveform data.
12. The method of claim 1, further comprising the step of displaying waveform segments corresponding to repeat vectors.
13. The method of claim 1, further comprising the step of displaying waveform data segments of multiple vector periods per display division.
14. The method of claim 1, wherein probing a net of the device comprises applying a focused particle beam to the net and detecting secondary particles.
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Type: Grant
Filed: Jul 17, 1995
Date of Patent: Mar 24, 1998
Assignee: Schlumberger Technologies Inc. (San Jose, CA)
Inventor: Peter Frank Ullmann (San Jose, CA)
Primary Examiner: Emanual T. Voeltz
Assistant Examiner: Demetra R. Smith
Attorney: Bruce D. Riter
Application Number: 8/503,023
International Classification: G01R 3128;
